92 S10 Blazer 4x4 4.3L TBI

[Wags391]

This is how the progression went: First, my Blazer would die when going in reverse. Then it would die when starting, but go after 2 or 3 starts. Then it starting dying on the road. Now it will run for 2-5 seconds and shut off as if I turned it off.

Already checked Dist. Control Mod., EGR valve, and MAP sensor. They are all good.

Funny thing is: When I decided to check the Fuel Pump relay, I was able to remove the relay and the car would start and stay running. Then I put it back on and it would shut off.

So I believe I have answered my own question, but wanted to be sure. I think my next course of action would be to check the wiring from the relay.

Any other suggestions?

[MT-2500]

Kinda of a strange problem.
Remember the fuel pump runs off of oil pressure switch if fuel pump relay fails when running.
Does it shut off from fuel pump quiting or low fuel pressure or lose of spark?
MT

[Wags391]

I don't know why is shuts off. I would guess, from the sound of it, that the fuel pump is shutting off. Today I tried this: I unplugged the Oil Pressure Switch, jumped the orange and gray and grounded the other. This seemed to make the pump run double-time but it got it running and kept running. Once the engine became warm, I could stop and restart the engine without a problem. Once the engine became cool, it began to die again. Would this be a problem with the Oil Switch?

[MT-2500]

To check oil pressure switch with truck running unplug fuel pump relay and is it stays running your oil pressure switch is working.

Check fuel pump gray wire for voltage when it quits.
Or if it does not quit with fuel pump gray wire jumped.
You have a relay or oil pressure switch problem.
Good luck
MT

[Wags391]

Went to check my timing today and I could not find the mark on the harmonic balancer with the light on plug 1. Attached the light to plug 2 and found the mark. How is that my timing is set to the #2 cylinder? I've always gone off of #1. I recently had my transmission rebuilt. What did they do!?

[Wags391]

Here is the latest: replaced Fuel Pump Relay and the Oil Pressure Switch. Still no good. So it's not the MAP sensor, Pump relay, Oil Switch, and no codes have been thrown. I took off both the relay and the switch and put on jumper wires into the pigtails and I can get it to run fine. That leads me to believe that it is not a bad wire somewhere. If I let it warm up to operating temperature and then put the relay and switch back on then it works fine. As soon as it cools down, back to shutting off after two to five seconds.

My next, and scary thought, is the computer itself. What are the chances of that?

[Wags391]

Here is the latest: replaced Fuel Pump Relay and the Oil Pressure Switch. Still no good. So it's not the MAP sensor, Pump relay, Oil Switch, and no codes have been thrown. I took off both the relay and the switch and put on jumper wires into the pigtails and I can get it to run fine. That leads me to believe that it is not a bad wire somewhere. If I let it warm up to operating temperature and then put the relay and switch back on then it works fine. As soon as it cools down, back to shutting off after two to five seconds.

My next, and scary thought, is the computer itself. What are the chances of that?

[MT-2500]

Originally Posted by Wags391

Here is the latest: replaced Fuel Pump Relay and the Oil Pressure Switch. Still no good. So it's not the MAP sensor, Pump relay, Oil Switch, and no codes have been thrown. I took off both the relay and the switch and put on jumper wires into the pigtails and I can get it to run fine. That leads me to believe that it is not a bad wire somewhere. If I let it warm up to operating temperature and then put the relay and switch back on then it works fine. As soon as it cools down, back to shutting off after two to five seconds.

My next, and scary thought, is the computer itself. What are the chances of that?

Yes and no on the computer.
Pull it down and give it the old tap twist it test.
Good luck
Mt

[rhandwor]

Try unplugging the computer cleaning the connections with electrical contact cleaner.
I would also clean the grounds for the relays and computer system.

[Wags391]

Is the ECM accessible without taking out the dash? I replaced my heater core once and it looked as though I would have to do the same procedure to remove the computer.

[Wags391]

Got the ECM out today. Cleaning the connections and wiggled wires. All ground wires seemed to be fine. Still shutting down on me after a couple of seconds. I figure the next things to do is to check out the computer. How should I go about doing that? Getting the PROM reprogrammed? Sending the entire ECM in to be redone? Maybe go ahead and purchase a performance chip? Suggestions, please.

[MT-2500]

Tap and wiggle and twist and whack it works best on a pcm test.


I would make sure the ign module is not losing spark when it does it.
You have to have good spark and RPM signal for the pcm to run fuel pump.
MT

[axlemaker]

This may be a wild thought but I wonder if anyone has suggested the "sock" on the pick-up tube -- sounds like the sock is collapsing and stopping fuel flow -- going to reverse - a possible surge or "slosh" of fuel against the sock.

[Wags391]

I'm going to try a little more wiggling and whacking. What is the white box locating directing on the ECM? It has two connectors going to it. Just curious.

[Wags391]

I'm going to try a little more wiggling and whacking. What is the white box locating directing on the ECM? It has two connectors going to it. Just curious.